1. Field of the Invention
The present invention relates to an information input/output control device and a method therefor which executes a required functional operation by converting data having the first data format needed to be processed into the data having the second data format and by outputting the data having the second data format at a designated information terminal in a network environment under which plural kinds of information terminals are available to be used.
2. Related Background Art
This kind of terminal devices, particularly printers, have been directly connected with a host computer through a parallel interface called as Centronics or through a serial interface called as RS-232C.
Scanners (document reading device) have been directly connected to the computer through a non-standard video interface or through a SCSI interface.
Under the above interfaces, each computer must be connected both a printer and a scanner to realize an excellent utilization environment, which fails to use the source efficiently. Since it was practically impossible for all computers to be connected with a printer and a scanner, other computers have been borrowed with a floppy disk or a Centronics branch box has been commonly used for character base printers.
A new development of network technology has recently commercialized a printer incorporating therein a LAN interface. Any computer in the network can easily print data by connecting the computers with the printers through the LAN.
These network printers have mostly incorporated thereinto Post Script, a page description language developed by Adobe Co., Ltd. in U.S.A. and almost quasi-standardized in the market.
Programs have been such constructed to have multi-tasks (multi-processes) by dividing the conventional communication protocol structure into a plurality of layers, each of which has an independent packet format and is assigned to its own tasks (processes) so that a function of each layers is clearized, thereby facilitating an independent design. There is also an advantage that a lower layer can concentrate into providing a service entity to a higher layer.
Further, a stand alone type scanner or printer has been utilized in a manner that it is directly connected with a host computer. Since an integral type scanner/printer has been generally utilized as a copier, it has not been utilized in a manner that it serves a scanner printer server when connected with a network.
On the other hand, there has been a structure in which a printer is connected with a printer server in the network and is commonly utilized.
Under such a printer server, data has been usually transmitted from the host computer to satisfy a specification of the printer.
There has been conventionally no method for using a network scanner with which scanning operations are performed by a remote host connected to the network.
Accordingly, the host device requesting a scanning operation must have fed a video image from a scanner connected to the host computer itself. Alternatively, the video image was read from the scanner connected with the other host computer in the network and transferred to the requesting host through the network.
When the video image fed by the scanner is printed out together with the other informations, such as characters, drawings etc., the scanned video image and the other informations are usually synthesized in the host device requesting the printing operation and output to a printer connected to the network.
There have been the following kinds of data processing method in a conventional server device.
(1) The video image data expanded into a bit image format in the host is transferred from the host to the printer through an exclusive user interface. The host takes care of all the interface operations with the network. This method has been mainly utilized in an intelligent host, such as a work station.
(2) The host transmits only a page description language. The printer incorporating an interpreter function converts it into a bit image format, which is so called as a network printer.
(3) The device, which converts a page description language transmitted from the host into an exclusive user bit image, further transmits the image data to a printer through an exclusive use interface.
There have been frequently used the following down load methods for a seven device existing in a conventional network.
(a) Necessary programs have been down loaded from a down load host when the server device is activated.
(b) Fonts, filters and the like have been down loaded by the host computer requesting a printing procedure to a printer.
NIS (Network Information System), which has been widly utilized under a UNIX environment, has been used, as a parameter management system under a conventional network environment, in order to control hosts and users in the network.
In the NIS, a master server device, a slave server device and a client are provided in a domain of the network and parameters for controlling hosts or users in the domain are usually managed by the master server.
An alteration information of the master server is automatically transferred to the slaver server. Accordingly, the parameter information can be referred without being aware of the master server device and the slave server device.
However, in case of connecting a printer, which can be commonly used, with the network in the system constructed by utilizing the page description language, namely, in case of connecting a printer without restriction by standardizing the network printer interface, there are two principles.
1 An application software must not depend on languages or control methods for each printer.
2 A printer does not care the difference of codes output by each application.
As being such above, there must exist a mechanism which absorbs the usage difference between the both application software and printer, namely, a printer driver (Program).
In using the post script, since the application software outputs a script code and the printer interpretes the post script, a printing can be normally accomplished. In other words, it can be said that the application software depends on the post script of a printer language and the printer depends on the post script code output by the application software.
The post script is dedicated to a printer and not utilized for a scanner.
In this manner, when a scanner request and a printer request from each host computer have been attempted to be processed by utilizing, as a common resource, a scanner printer (copier) having a scanner and a printer, the application software may encounter with some restrictions due to the usage restriction of the post script, thereby unabling to practice the specification of the scanner printer.
Further, when a protocol in the communication network is constituted as a layer structure, a task to task communication, which has not been used in a fundamental inter network communication, will increase so that the CPU becomes over-loaded in processing and data processing efficiency will be reduced.
There also arises a problem to consume memory resources because each task consumes buffer memories.
There has been recently developing a network, for example, a large scale network in which LAN (Local Area Network) is stretched around in an intelligent building.
There has been also developing a world wide network, namely, WAN (Wide Area Network) directly connecting the LAN with the public communication line, and further a high intelligence information network like ISDN.
Accordingly, it has been becoming possible that a host computer installed at a certain floor in the building can be accessed from the other floor of the same building or even from the other building, and that a host computer located in Tokyo can be accessed from Osaka, so that the printer server can be widely utilized in comparison with the limited usage in the past.
A scanner and a printer have been also progressing to a direction with an intelligent function, a high resolution and a color, so that a document can be read from various types of scanners and output at any printer.
In a conventional scanner or a printer, which is directly connected with a host computer, the host computer has been setting each terminal device and inputting/outputting video image data. There has been no problem to employ independently within a system an own interface (I/F), a video image format, a communication speed and the like because each host computer has corresponded to each terminal device.
On the other hand, since a scanner and a printer connected with the network through an SP server system can be utilized by a plurality of host computers, there have been advantage to commonly use the resources and to provide a common utilization environment to various types of host computers, thereby being efficient.
However, since the terminal devices have been commonly utilized in the network, there arises the following new problem.
Firstly, the terminal devices are utilized with various different times and sometimes simultaneously with each other. When a user B issues a request for using a printer while a user B has been using the printer through an SP server system, it is doutful whether the SP server provides the users A and B with the same service.
Secondly, when an error occurs while a user A has been using a printer in the same way described above, it may cause some problems how to inform the user A of the error or how a user B should be informed that the printer is not available.
Thirdly, when a mulfunction occurs either on the SP server system or the host computer, communication between the SP server system and the host computer will be disconnected so that either one will become a command waiting state thereby causing dead lock of the system.
A timer watching function may be employed to avoid the above described phenomenon. In this case, a response to each command has been waited for a predetermined period of time and resending requests will be issued several times whenever the predetermined period of time lapses. If no response has been received, the communication will be terminated and initializing procedure will be performed.
However, the above communication control encounters the following new problems.
In a large scale network in which a network is connected with the other networks through a gate way or a router and an SP server system connected to a scanner and a printer and a host computer are respectively located in different networks with each other, a predetermined time set by a timer watching function happens to lapse if either one of the networks functions with a delay to the other one even though a response to each command reveals normal. The above phenomenon will occur if a delay is substantial among the gateways or the routers and if either one of networks is abnormally crowded.
When the above phenomenon would happen, even though a normal communication has been performed with a large communication delay between the networks, the SP server system or the host computer actuates the timer watching function to issue a resending request automatically, thereby the network being initialized automatically.
Accordingly, there has been a problem that users cannot utilize resources, that is, a scanner or a printer even in a normal communication.
Further in a data down load method and a parameter managing method in a conventional server device, a down loading procedure and its management to a program, a filter, a font, a parameter and the like have not been conducted by a commonly used device in a domain of the network, when viewed from a specific server device (in the above case, a master and a slave independently perform the down loading procedure or the like).
Accordingly, there arises a problem how to deal with a down load and a parameter management for a server device processing a scanner request and a printer request from each client, with a scanner printer being connected to the network.
In other words, when a scanner/printer (S/P) server device is disposed in the network, the conventional data down loading method and parameter management method cannot instruct the S/P server device to manage the program, the filter, the font and the parameter totally so that the S/P server device cannot cope with an unexpected break down of the system.
When a master host and a slave host are set among a plurality of down loaded hosts, since a mutual communication between the slave hosts has not been made, the alternation of the parameter, and the like cannot be possible if the master host would happen to break down, which prohibits to provide a system service.